In general terms, the present invention relates to MEMS components in whose layer structure at least one self-supporting structural element having at least one electrode is realized.
The self-supporting structural element may be a micromechanical component which has its own sensor or actuator functionality, for instance the diaphragm of a pressure sensor, a microphone or an amplifier. However, the self-supporting structural element may also serve simply as a carrier for a sensor functionality, for instance in the case of a flow-rate sensor having heating resistors which are present on a diaphragm for the thermal decoupling. Accordingly, the electrode of the self-supporting structural element may be utilized as a capacitor electrode for acquiring measuring signals or for the excitation of vibrations or also simply for the electrical contacting of an electrical resistor or some other circuit component. In all cases, leakage currents between the electrode and the abutting carrier material of the structural element have a detrimental effect on the component function.
The micromechanical structure of MEMS components is usually realized in the form of a layer structure which is the result of a sequence of layer depositing processes and structuring processes. Self-supporting structures are produced either in a back-etching process or within the framework of front-side processing in a sacrificial-layer etching process. In both cases, the use of an etch-stop layer for the physical restriction of the etching process is advantageous. This allows for the realization of structural elements of a specifiable defined geometry and more specifically, also the realization of very thin-walled structural elements such as diaphragms and bending beams.
The self-supporting structural element should be developed in one layer or in multiple layers whose mechanical properties correspond to or accommodate the function of the structural element. For instance, a self-supporting structural element that is to be used as a sensor or microphone diaphragm should be as thin and elastic as possible, while the stationary counterelement of a microphone structure must have the highest rigidity possible.